Weather Blog: Rounds of heavy rain ahead

***UPDATE*** Flood watch issued for all of Southeastern Wisconsin from Wednesday afternoon through Friday morning. Major river flooding is possible.

Thank you for stopping by the Weather Watch 12 Blog! After a one day break from rain, a large storm system will deliver more potentially heavy rain to southeastern Wisconsin. In today's blog we look at when the heaviest rain falls, and the locations that may see 3" or more by Friday.

Today's dry weather will help saturated levels and swollen rivers very little. That means more flooding is likely if the forecast plays out as expected in the coming days.

The first round of rain arrives late Wednesday morning/afternoon. Futurecast below shows yellow on the forecast radar indicating a steady if not heavy period of rain. This area of rain will exit by late afternoon or evening.

A second more impressive round begins Wednesday night or Thursday morning. Low pressure will ride along a nearly stationary front delivering a surge of moisture. This round of rain and thunderstorms will likely produce some heavy rain. The GFS computer model forecast below is valid at 7am. The dark blue colors represent forecast rainfall totals over a 3 hour window of 0.50"-1".

A potential break in the rain may occur midday Thursday or Thursday afternoon. Any break will be short-lived with the main area of low pressure lifting north Thursday evening/night. Another round of heavy rain is possible during this timeframe. The GFS computer model forecast below is valid at 10pm Thursday.

The exact track of the lows will be key in determining just how much rain will see by Friday morning. Let's take a look at two different rainfall forecasts from Wednesday-Friday morning. First, the GFS below shows a general area of 2"-2.75" across southeast Wisconsin.

The RPM forecast below produces higher totals of 3"-5"+ for much of our area. The top end totals of this forecast may be a little high. To get totals around 5"+ we would need all three rounds to hit southeast Wisconsin, and thunderstorms to also occur to enhance the rainfall rates. We need to monitor this very closely as any periods of heavy rain will likely send rivers over flood stage once again.

As colder temperatures wrap into the system on Friday the rain may mix with or change to snow. Still too early to tell if any part of southern Wisconsin will see snow accumulation. Snow accumulation this late in April can still happen, and in fact if we pick up more than 0.1" on Friday it would be a daily snowfall record.

Enjoy the dry weather now, as more cool, damp and dreary weather is about to return.

For the latest weather information watch WISN 12 News, and for updates throughout the day follow me on Twitter @jnelsonweather